The Big Bang, the LHC and the Higgs Boson Dr Cormac O’ Raifeartaigh (WIT)

Overview I. LHC What, How and Why II. Particle physics The Standard Model III. LHC Expectations T he Higgs boson and beyond Big Bang cosmology

The Large Hadron Collider N o black holes High-energy proton beams Opposite directions Huge energy of collision Create short-lived particles E = mc 2 Detection and measurement

How E = 14 TeV λ =1 x m Ultra high vacuum Low temp: 1.6 K LEP tunnel: 27 km 1200 superconducting magnets 600 M collisions/sec

Why Explore fundamental constituents of matter Investigate inter-relation of forces that hold matter together Glimpse of early universe Highest energy since BB Mystery of dark matter Mystery of antimatter T = K t = 1x s V = football

Cosmology E = kT → T =

Particle cosmology

Particle detectors 4 main detectors CMS multi-purpose ATLAS multi-purpose ALICE quark-gluon plasma LHC-b antimatter decay

Particle detectors Tracking device measures momentum of charged particle Calorimeter measures energy of particle by absorption Identification detector measures velocity of particle by Cherenkov radiation

II Particle physics (1930s) electron (1895) proton (1909) nuclear atom (1911) RBS what holds nucleus together? what holds electrons in place? what causes radioactivity? Periodic Table: protons (1918) neutron (1932)

Four forces of nature Force of gravity Holds cosmos together Long range Electromagnetic force Holds atoms together Strong nuclear force: holds nucleus together Weak nuclear force: Beta decay The atom

Strong force SF >> em charge indep protons, neutrons short range HUP massive particle Yukawa pion 3 charge states

New particles (1950s) Cosmic raysParticle accelerators cyclotron π + → μ + + ν

Particle Zoo (1960s) Over 100 particles

Quarks (1960s) new periodic table p +,n not fundamental symmetry arguments (SU3 gauge symmetry) SU3 → quarks new fundamental particles UP and DOWN prediction of  - Stanford experiments 1969 Gell-Mann, Zweig

Quantum chromodynamics scattering experiments colour SF = chromodynamics asymptotic freedom confinement infra-red slavery The energy required to produce a separation far exceeds the pair production energy of a quark-antiquark pair,pair production energy

Quark generations Six different quarks (u,d,s,c,t,b) Six leptons (e, μ, τ, υ e, υ μ, υ τ ) Gen I: all of matter Gen II, III redundant

Electro-weak interaction Gauge theory of em and w interaction Salaam, Weinberg, Glashow Above 100 GeV Interactions of leptons by exchange of W,Z bosons Higgs mechanism to generate mass Predictions Weak neutral currents (1973) W and Z gauge bosons (CERN, 1983) Higgs boson

The Origin of Mass The strong nuclear force cannot explain the mass of the electron though… The Higgs Boson We suspect the vacuum is full of another sort of matter that is responsible – the higgs…. a new sort of matter – a scalar? Or very heavy quarks top mass = 175 proton mass To explain the W mass the higgs vacuum must be 100 times denser than nuclear matter!! It must be weak charged but not electrically charged

The Standard Model (1970s) Strong force = quark force (QCD) EM + weak force = electroweak Matter particles: fermions (quarks and leptons) Force particles: bosons Prediction: W +-,Z 0 boson Detected: CERN, 1983

Standard Model : 1980s Experimental success but Higgs boson outstanding Key particle: too heavy?

III LHC expectations (SM) Higgs boson Determines mass of other particles GeV Set by mass of top quark, Z boson Search…surprise?

Main production mechanisms of the Higgs at the LHC Ref: A. Djouadi, hep-ph/

For low Higgs mass m h  150 GeV, the Higgs mostly decays to two b-quarks, two tau leptons, two gluons and etc. In hadron colliders these modes are difficult to extract because of the large QCD jet background. The silver detection mode in this mass range is the two photons mode: h  , which like the gluon fusion is a loop-induced process. Higgs decay channels

Decay channels depend on the Higgs mass: Ref: A. Djouadi, hep-ph/

Ref: hep-ph/ A summary plot:

Expectations: Beyond the SM Unified field theory Grand unified theory (GUT): 3 forces Theory of everything (TOE): 4 forces Supersymmetry symmetry of fermions and bosons improves GUT makes TOE possible Phenomenology Supersymmetric particles? Not observed: broken symmetry

IV Expectations: cosmology √ 1. Exotic particles:S √ 2. Unification of forces 3. Nature of dark matter? neutralinos? 4. Missing antimatter? LHCb High E = photo of early U 1. Unification of forces: SUSY 2. SUSY = dark matter? double whammy 3. Matter/antimatter asymmetry? LHCb

Particle cosmology

LHCb Tangential to ring B-meson collection Decay of b quark, antiquark CP violation (UCD group) Where is antimatter? Asymmetry in M/AM decay CP violation Quantum loops

Summary Higgs boson Close chapter on SM Supersymmetric particles Open new chapter: TOE Cosmology Nature of Dark Matter Missing antimatter Unexpected particles? New avenues

Epilogue: CERN and Ireland World leader 20 member states 10 associate states 80 nations, 500 univ. Ireland not a member No particle physics in Ireland European Organization for Nuclear Research